(1) Field of the Invention
This invention relates to a disposable grounding strap for shoes for the purpose of preventing the accumulation of static electricity on personnel who are engaged in vocations such as assembly or fabrication of electronic components, operation of computer systems, and in potentially hazardous environments where there is a possibility of explosive atmospheric conditions, for example, operating rooms utilizing flammable anaesthetics, the manufacture or distribution of flammable liquids or gasses, etc.
The strap is a narrow flexible conductive article with one end positioned to the upper edge of a wearer's shoe by means of an elongated metal strip and the opposite end secured by pressure-sensitive adhesive to the sole or heel of the wearer's shoe.
(2) Description of the Prior Art
There are numerous shoe grounding devices in the prior art. For example, W. C. Legge has a series of patents such as U.S. Pat. No. 2,933,651, issued Apr. 19, 1960 showing a strap which buckles to a wearer's leg and electrically connected to a grounding device strapped to a shoe; U.S. Pat. No. 3,379,932 issued Apr. 23, 1968 for a similar device which has means to adjust straps around the wearer's leg and shoe; and U.S. Pat. No. 3,775,509 issued Apr. 9, 1968 which shows a grounding device secured by straps to a shoe with grounding contact made to the floor by means of a conductive flexible tube. However, all of the Legge devices require manipulation of buckles or straps to one's shoe and leg and adjustment of wires which conduct static charges from the wearer's body to the grounding device.
U.S. Pat. No. 3,993,932 to Weigl issued Nov. 23, 1976 utilizes a grounding web integrally formed with a shoe sole.
In addition to various mechanically adjusted strapping devices for antistatic footwear, pressure-sensitive adhesives have been used to adhere the grounding strap to the bottom of a shoe and to assist in the connection of a free end of the strap to the ankle or lower leg of the wearer.
For example, U.S. Pat. No. 3,832,598 to Oehmke issued Aug. 27, 1974 illustrates a shoe strap consisting of a flexible conductive backing with a pressure-sensitive adhesive covered by a release liner. The adhesive adheres the strap to the bottom of the shoe upon removal of the liner. The free end of the strap is also secured by an adhesive on the wearer's ankle.
The patent to Hines U.S. Pat. No. 2,785,344 issued Mar. 12, 1957 also utilizes a pressure-sensitive adhesive. Here the grounding strap consists of two parts joined by a fastener 10 so that the lower portion of the strap which adheres to the heel of the shoe can be discarded or replaced. Both the lower and upper part of the strap are adhered by an adhesive which is coated onto a flexible backing to form the surface of the strap which interfaces with and adheres to the wearer's shoe.
One problem with adhesive grounding straps in the prior art is that they require the use and removal of protective liners. Once the liner is removed and the adhesive surface is exposed for positioning on the shoe, the tacky surface renders the strap difficult to handle and difficult to precisely position on the shoe heel or sole. Further if the strap and adhesive coated thereon extend up the sides of the shoe and/or are made in comparatively long lengths to fit a wide range of shoe sizes and shapes, the exposed adhesive may contact the sides of the shoe and possibly damage the shoe when the strap is removed.